Locking down the plunger of a pump is highly desirable after the pump has been installed on a product-filled container and is prepared for shipment. In the locked-down position, considerably less space is occupied by the pump than when the plunger is fully extended, thereby resulting in significant savings in terms of packaging, shipment and eventual display on merchandising shelves. Moreover, locking down the plunger aids in effecting proper seals to prevent accidental leakage of the product in the event that the container is laid on its side or inverted.
Once the plunger is in its locked-down position, it is important that the plunger be very stably retained, inasmuch as wobbling or rocking of the plunger may have a deleterious effect upon the quality of various fluid-tight seals which are effected at this time. Moreover, it is important that the plunger be locked down in a manner to impart a predetermined amount of compressive loading at such various seal points in order to assure that the intended safeguards against leakage are indeed implemented.
While it is generally desirable, then, to achieve a locked-down capability, at the same time, it is important that this feature not interfere with and adversely affect the dispensation of predictable, uniform doses or portions of product during each pumping stroke of the unit. In this regard, the position in which the plunger is actually locked down represents a somewhat further depressed position of the plunger beyond that normally attained during pumping operations. If appropriate measures are not taken, the user might rather easily depress the plunger further than intended by the manufacturer to the full extreme desired only in locking situations, such additional stroke length resulting in a greater-than-intended dose or portion size being dispensed.
Additionally, many of the product containers with which pumps of this type are utilized have a transverse elongation or ovality which is taken into consideration during packaging with other of the units in bulk for shipment. Desirably, such containers are packed with their elongations oriented in the same manner and, in those units where projecting dispensing spouts are utilized, such spouts are likewise desirably oriented to project in the direction of elongation of the containers. It is necessary in such instances for the plungers to be locked down, yet so designed that their spouts can still be reoriented in this manner.